Tsunami Detection from Space using GNSS Reflections

Transcription

1 Tsunami Detection from Space using GNSS Reflections R. Stosius, G. Beyerle, A. Helm, A. Hoechner, and J. Wickert Nat. Hazards Earth Syst. Sci., 10, ,

2 Tsunami Detection from Space Global Tsunami Sources 1650 B.C. to A.D from Earthquake, Volcano, Landslide, and Other Causes, Intergovernmental Oceanographic Commission, Paris, United Nations Educational, Scientific, and Cultural Organization (UNESCO). IOC Technical Series, 85, Tsunamis are a global phenomenon Satellites are predestined for global monitoring 6

3 Tsunami Detection from Space Tsunamis are a global phenomenon Satellites are predestined for global monitoring 7

4 Tsunami Detection from Space Radar Altimetry (RA) Tsunami detection with RA demonstrated for Sumatra tsunami Only few satellites Data transmission only once per orbit Measurments only along track Left: Measured and modelled sea surface anomalie (SLA) of 60 cm for JASON-1 pass 129, 1:53 hour after the earthquake that generated the Sumatra tsunami (right). Ablain, M. et al. (2006): The Indian Ocean Tsunami of December 26, 2004, Observed by Multi-Satellite Altimetry, 15 years of Progress in Radar Altimetry, Venice,

5 Tsunami Detection from Space eflectometry () Code Altimetry Delay as a measure between direct and Martín-Neira, A Passive Reflectometry and Interferometry System (PARIS): Application to Ocean Altimetry, ESA J., vol.17, pp , 1993 reflected path travel time 9

6 Tsunami Detection from Space eflectometry () Phase Altimetry LEO GNSS The interference of the phase shift between direct and coherently Earth troposphere ionosphere reflected signal can be translated into height variations Depends on surface roughness and grazing elevation angles 10

7 Comparison of Two Configurations Code Altimetry Phase Altimetry PARIS concept Coherent reflectometry concept Zenith and nadir antenna, Fore and aft looking antenna, 60 halfangle in azimuth Omnidirectional in azimuth Reflection path elevation Reflection path elevation < 5 > 35 code altimetry footprint phase altimetry footprints 11

8 Detection Simulation Assumtions on Low Earth Orbit (LEO) satellites Walker constellation (e.g. 18/3 means 18 satellites on 3 orbits) Omnidirectional antenna configuration to receive reflections at all possible elevation and azimuth angles GPS, GLONASS, and Galileo available as signal sources 20 centimeter altimetric sensitivity to detect tsunami waves (anomalies) of 20 cm and higher, technical feasibility provided 12

9 Tsunami Wave Propagation Model Sumatra tsunami, , M 9.1 TUNAMI-N2 tsunami wave propagation model 5 arcmin spatial grid, 1 min resolution, 3 hours period Reflection point ground tracks crossing the tsunami area 13

10 Tsunami Detection Simulation Count number of grid cells crossed by ground tracks matching the sensitivity criterion of 20 cm for each time step Repeat 100 times with random start time because start of event is unknown a priori Cumulate first detections Simulation parameters: 18/3 constellation, 900 km alt., 60 inc., Sumatra tsunami, 20cm sensitivity, omnidirectional view Results: 98% detection probability after 15min when using all GNSS together as source 14

11 Andaman and Amorgos Tsunami Andaman, Indian Ocean, 1941 Amorgos, Mediterranen, 1956 landslides Medium event M 8.1 Largest event in the Aegan Sea in 20th century M 7.8 Slides near Astypalaia and Folegandros 15

12 Andaman and Amorgos Tsunami 91% detection prob. for Andaman event after 15 min using 48/8 First detections of Amorgos event after 27 min Similar detection performance when detecting slides only 16

13 Activities from GFZ Lake Walchen Experiment GPS-SIDS Waveform and phase measurements with the OpenGPS and the GNSS Occultation Reflectometry Scatterometry (GORS) receiver prototype, a modified geodetic JAVAD receiver GPS Sea Ice-Dry Snow Experiment Winter 2008/2009 Godhavn, Disko Bay, Western Greenland Cliff 670m above sea level Phase altimetry: semidiurnal tides 17

14 ZOIS (Zeppelin Occultation Interferometry Scatterometry) measurments by GFZ and DLR on board of the Zeppelin NT. Zenit and sidelooking antennas at rear engine, nadir antenna at cabin. Next measurement flight scheduled for October over Lake Constance. 18

15 GEOHALO High Altitude and LOng Range (HALO) research aircraft GEOHALO: Gravity, Magnetik and Foto: A. Minikin, DLR eflectometry, Scatterometry & Radio Occultation Aegan Sea, Mediterranean, 2012 Status: Certification process started Simulation of GNSS reflections reaching HALO during flight 19

16 MicroGEM Phase A/0 Study GPS-Reflections, Galileo-Reflections, Occultations, TEC, VLBI, SLR and Downlink. 20

17 Conclusions Simulations show that tsunamis are detectable with LEO satellite constellations within 15 minutes The detection performance for tsunamis in the Indian Ocean is good also for medium tsunamis but poor even for strong tsunamis in the Mediterranean. GFZ is active in several ground based, airborne and spaceborne experiments to develop a space borne system that can be the basis for a future global tsunami early warning system 21

18 Thank you for your attention 22

19 Reflection Point Calculation Reflection point calculation for WGS84 using ray path minimization like in Garrison et al.,

20 Tsunami Detection Performance Cummulation of first detections defines detection probability Detection performance is high when probability function is steep The detection probability function results are significant Detection probability functions of 24 different calculations for the Sumatra tsunami based on 18/3 Walker constellation at 900 km and with 60 inclination, with all GNSS reflections available. 24

21 LEO Walker Constellation Scenarios 1800 km orbit altitude inclination angle km 900 km 600 km 450 km 350 km Orbit planes Satellites per orbit Satellites

22 LEO Constellations 18/3 Walker constellation with 60 inclination. Temporal coverage can be increased by using a LEO satellite constellation 18/3 Walker constellation with 120 (retrograde) inclination. GPS reflection point coverage of several types of constellations Two 9/3 Walker constellations with 40 (blue) and 80 (red) inclination. with 18 satellites investigated Walker constellations show Meshed-comb constellation with 60 inclination (every second orbit s mean anomaly is shifted by 180 ). best reflection point coverage 26

23 Magnitude Dependency of Detection Good strong tsunami detection Only % within first 30 minutes for medium tsunamis Week / local tsunamis not detectable 27

24 Dependency from Altimetric Sensitivity Tsunami detection simulation with various altimetric sensitivities For Sumatra tsunami the detection performance is good up to 100 cm but for Nias tsunami it should be 50 cm within first 15 minutes 28

25 Comparison of Various Scenarios code phase Performance increases with number of satellites and orbit altitude Within 15 min both perform similar but performance is low low orbits and few satellites phase altimetry performs better 29

26 Downlink Concept Onboard processing, transmission of suspicious tracks via geostationary communication satellites when satellite reaches equator region Downlink at stations installed in endangered regions 30